This image of a sand dune field in a Southern highlands crater was acquired when the Sun was just 5 degrees above the horizon. As a result, the image is mostly shadows, with sharply-delineated dune crests sticking up into the sunlight.
The especially bright patches—bluish in enhanced color—are due to seasonal frost that is accumulating as this hemisphere approaches winter.
Photo credit: NASA/JPL/University of Arizona
Note: For more information, see PIA18118: Dramatic Dune Destination. This impact crater is located just east of Proctor Crater.